This invention relates to a system for synchronizing the collar and gear of heavy vehicle transmissions that operates using an electronic monitor and a frictional member.
Typically in heavy transmissions, there is a main gear box and an auxiliary box. The auxiliary box may be a range box, a splitter box, or a combination. In an auxiliary box the gear speeds are typically changed by moving a sliding element, which may be known as a collar, between a position where it engages a first gear, and a position where it engages a second gear. As this movement is completed, it becomes necessary for the collar and the gear which is to be engaged to approach a similar speed, or to be xe2x80x9csynchronizedxe2x80x9d. The system now used to synchronize the RPM of the collar and gear uses a synchronizing pin that mechanically blocks the collar from engaging the gear until the RPM of collar and gear are equalized. These synchronizing pins are usually quite costly because the parts require tight tolerances. Generally, the synchronizers require close positioning, and result in vibration, etc. if the components are offset or out of tolerance. Further, the synchronizer pins are susceptible to failure when drive lines are not set up properly, and may induce a vibration into the transmission.
More recently, assisted shift systems have been developed which control engine output such that the speed of rotating components to be brought into engagement, reach a synchronized speed for the next gear. With such systems, monitoring of actual shaft speed is utilized.
The creation of a synchronizer system that does not use pins to block engagement until the collar and gear RPM are equalized, would be desirable.
In a disclosed embodiment of this invention, a synchronizing assembly includes a rotatable collar, a rotatable gear, and a friction element positioned between the two. The friction element is splined to the collar but is free to move axially. A set of springs is positioned between the collar and the friction element. The gear has a machined surface to receive the adjacent friction element. A transmission control unit monitors the speed of the collar and gear. The axial position of the collar is also monitored by the transmission control unit. When gear change is initiated, a control valve is energized causing the collar to move axially toward the gear. The collar moves until the friction element contacts the gear surface. Preferably, the control valve is then modulated causing brief momentary contact of the gear and friction element. A frictional torque is created which causes equalization of collar and gear speed. Collar and gear speed continue to be monitored by the transmission control unit until they are equal, or at least within a small predetermined maximum difference. At this point, the control valve is energized allowing the collar to compress the spring between it and the friction element and engage the gear. In a second embodiment, the friction element could also be controlled by a valve separate from the collar valve, eliminating the need for the springs.
The electronically monitored and frictionally induced equalizing of the gear and the collar of the synchronizer assembly of the present invention succeeds in synchronizing collar and gear speed without the use of a synchronizing pin. Thus, the invention eliminates the costly manufacture of high tolerance parts and reduces the incidence of failure due to improper drive line setup.
These and other features of the present invention can be understood from the following specification and drawings, the following of which is a brief description.